Essentially, Git keeps tabs on text changes, but the definition is a version control system. Chances are you've already used git one way or another: it is a de-facto standard for code versioning due to it's distributed nature, as opposed to centralised Apache Subversion (SVN).

In this tutorial we'll build a cyclic redundancy check (CRC) hashing function. More specifically, its 32 bit variant called "CRC-32". I bumped into it in the PNG specification, but it's also used in Gzip and bunch of other formats and protocols. In short, it makes a tiny (4 bytes) hash out of whatever binary data you feed to it and changes significantly if data changes even slightly. Of course, such a tiny function is not even close to be crypto secure, therefore it's only used to check if data was transferred correctly.

Binary is the very core of everything digital, not only in web development, but literally everything: from variables and file data to transport protocols and executables themselves.